PhD: Built for Performance in the Highest Degree4 Degree Elite Fit System: Uses two elastics for greater stretch and recovery to keep the sock in placeReliaWool: Patented ReliaWool technology in high impact areas provides superior durabilityMesh Venting: Men's-specific mesh ventilation zones provide additional breathability and moisture managementLight Elite Cushioning: Maximum impact protection with targeted cushioning on the ball and heel of the foot. Designed specifically for runners.Our best fitting, most advanced run socks yet, we packed years of testing, prototypes and running smarts into these socks. Featuring Light Elite cushioning in the ball and heel of the foot for ultimate shock absorption with minimal in-shoe volume, women's-specific mesh ventilation zones and a virtually seamless toe.Care: Machine Wash Warm Gentle Cycle. Do Not Bleach. Tumble Dry Low. Do Not Iron. Do Not Dry Clean.